Road pavers, which as an alternative are also referred to as asphalt finishers, bitumen road surface pavers or simply as pavers, are used in road construction and essentially serve for laying the road surface. To that end, the road paver draws a special tool, which is called a paving screed or floating screed, at a most constant speed along the planned path of the road to be constructed during operation (paving process). The screed steadily smoothens and partially compacts the paving material supplied to the ground for the road surface, which material may be (rolled) asphalt, for example. A road paver of such type having a screed is further described in DE 10 2011 018 469 A1, for example. The already described ideally continuous speed of the road paver during the paving process (paving speed) ensures that the road surface is applied uniformly and smoothened, while interruptions or major fluctuations of the paving speed may lead to a complication of the paving process and, at worst, to irregularities in the road surface, for example, as a result of the sagging of the screed into the applied road surface.
The amounts of material paved during the paving process are very large, a modern road paver may in fact pave several hundred tons of paving material within an hour. For this reason it has proven to be advantageous that the road paver is supplied by a series of trucks, particularly dumper trucks, during operation, which typically commute between an asphalt plant and the road paver. Depending on the throughput of the road paver, a dumper truck loaded with paving material may arrive at the road paver every two to five minutes in order to load the paver. However, since the loading process requires coordination of the two vehicles, in this arrangement there is a risk that the desired continuous paving speed is affected to an unbearable extent due to the frequent change of the loading vehicles.
For this reason, use of a so-called feeder in addition to the road paver and the dumper trucks has proven to be expedient. The feeder is a special-purpose vehicle having the task of enabling an uninterrupted supply of the road paver with paving material. To that end, the feeder forms a work train together with the road paver. During operation, said feeder drives in front of the road paver and assumes the role of a buffer for paving material. The dumper trucks supply the paving material to the feeder, which is thus to be coordinated with the dumper trucks. The paving material is temporarily stored in the feeder and passed over to the road paver, for example, by means of a conveyer belt on the feeder, during which process one end of the conveyor belt is placed over an open material storage (bunker) of the road paver. This way, the feeder may virtually buffer the speed fluctuations occurring due to the coordination with the dumper trucks for the road paver, so that the road paver can advance at a most constant speed and ideally only the feeder needs to vary its speed to some extent. For example, such feeders may be special-purpose machines exclusively provided for this task, or also modified road pavers as disclosed in EP 1 516 962 A2. Thus, the feeder is characterized essentially by its function within the work train.
However, during the paving process, road paver and feeder need to be coordinated as well. On the one hand, the road paver needs to stay on a predetermined path so that it paves the road surface as intended. As long as the feeder advances on the same path, this means that the road paver needs to follow the path of the feeder as precisely as possible. On the other hand, it needs to be ensured that the end of the conveyor belt of the feeder is placed over the bunker at any time and that the loading process between these two vehicles is performed as intended. To that end, the road paver needs to follow the feeder such that the material discharge from the feeder into the bunker of the paver is performed completely and reliably. In addition, this implicates that the distance between the feeder and the road paver must neither grow so large that the paving material supplied by the feeder is discharged in front of the road paver instead of into the bunker nor so small that the two vehicles collide or that the discharge of the paving material is effected to other areas of the road paver, such as the operator platform.
Currently, this problem is solved commonly by the machine operator (driver) of the road paver and the driver of the feeder. To that end, the driver of the road paver drives the road paver following the path of the feeder, for example. Since he has better view over the region between the two vehicles, particularly the region between the end of the conveyor belt and the bunker, the driver of the road paver also monitors the distance between the road paver and the feeder and, if required, signals to the driver of the feeder should the distance between the road paver and the feeder become too large or too small. In response to that, the driver of the feeder needs to accelerate or decelerate or adjust the steering in order to restore a most ideal distance between the feeder and the road paver.
The above-described method has several disadvantages. For example, the situation of the driver of the feeder is very demanding in that he needs to coordinate with both the driver of the dumper trucks in front of the feeder (for the loading process) and with the driver of the road paver behind the feeder at the same time, and in addition has to ensure that the feeder stays on the predetermined path. In turn, the driver of the paver needs to monitor the distance between the feeder and the paver, the direction of travel and the speed of the paver as well the paving process per se. Thus, this process involves two individual drivers during the paving process and is highly demanding for both drivers.